Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CEFACLOR vs AVYCAZ
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Bactericidal; inhibits cell wall synthesis by binding to penicillin-binding proteins (PBPs), disrupting peptidoglycan cross-linking.
AVYCAZ is a combination of ceftazidime, a cephalosporin beta-lactam antibiotic, and avibactam, a non-beta-lactam beta-lactamase inhibitor. Ceftazidime inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis. Avibactam protects ceftazidime from degradation by certain beta-lactamases, including Ambler class A, class C, and some class D enzymes.
Acute otitis media,Acute exacerbations of chronic bronchitis,Pharyngitis/tonsillitis,Uncomplicated skin and skin structure infections,Urinary tract infections,Lower respiratory tract infections including pneumonia
Complicated intra-abdominal infections (c IAI) in combination with metronidazole,Complicated urinary tract infections (c UTI) including pyelonephritis,Hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP)
250-500 mg orally every 8 hours
1 vial (ceftazidime 2g and avibactam 0.5g) IV over 2 hours every 8 hours.
Terminal elimination half-life: 0.5-1 hour; prolonged to 2-3 hours in renal impairment
Ceftazidime: ~2.8 hours; avibactam: ~2.7 hours. Extended in renal impairment (e.g., Cr Cl <50 m L/min requires dose adjustment).
Hepatic (minor); primarily renally excreted unchanged.
Ceftazidime is primarily excreted unchanged by the kidneys via glomerular filtration. Avibactam is also primarily eliminated renally and undergoes minimal metabolism. The metabolism of both components is not significantly mediated by cytochrome P450 enzymes.
Renal: 60-85% unchanged in urine within 8 hours; biliary/fecal: minor, ~5%
Ceftazidime: primarily renal (80-90% unchanged); avibactam: primarily renal (85-95% unchanged). Fecal excretion <1%.
25-50% bound to plasma proteins, primarily albumin
Ceftazidime: ~10% bound to albumin; avibactam: ~8% bound to human plasma proteins.
0.35-0.5 L/kg; distributes into most body tissues and fluids, including middle ear, sinus, and respiratory secretions
Ceftazidime: ~0.19 L/kg; avibactam: ~0.29 L/kg. Indicates extensive distribution into extracellular fluid.
Oral: 95% well absorbed; food does not significantly affect absorption
IV only; bioavailability is 100%.
Cr Cl 10-50 m L/min: 50% of usual dose every 8 hours; Cr Cl <10 m L/min: 50% of usual dose every 12 hours
Cr Cl 31-50 m L/min: 1 vial IV q8h; Cr Cl 16-30 m L/min: 1 vial IV q12h; Cr Cl 6-15 m L/min: 1 vial IV q24h; Cr Cl ≤5 m L/min: 1 vial IV q48h.
No adjustment required for mild to moderate hepatic impairment; safety in severe impairment not established
No dosage adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C).
20-40 mg/kg/day orally divided every 8 hours; maximum 1 g/day
Not approved for pediatric patients under 18 years of age.
No specific adjustment, but monitor renal function; initiate at lower end of dosing range due to age-related renal decline
Dose based on renal function, as per adult renal adjustment; no specific age-related adjustments.
None.
No black box warning for AVYCAZ.
Hypersensitivity reactions, including anaphylaxis,Clostridium difficile-associated diarrhea,Seizures (especially with renal impairment),Prolonged PT in patients on anticoagulants,False-positive urine glucose test
Hypersensitivity: Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported in patients receiving beta-lactam antibiotics.,Clostridioides difficile-associated diarrhea (CDAD): Has been reported with nearly all antibacterial agents and may range in severity from mild diarrhea to fatal colitis.,Direct Coombs test seroconversion: Positive direct Coombs test may develop during treatment, potentially interfering with crossmatching.,Central nervous system (CNS) adverse reactions: Including seizures, encephalopathy, and myoclonus have been reported, particularly in patients with renal impairment or higher doses.,Renal impairment: Dose adjustment required based on creatinine clearance.,Hepatotoxicity: Elevations of liver enzymes have been observed.,Nephrotoxicity: Concurrent use with nephrotoxic agents may increase risk.
Known hypersensitivity to cephalosporins or any component,Previous immediate hypersensitivity reaction to penicillins (cross-sensitivity)
Known hypersensitivity to ceftazidime, avibactam, or other cephalosporins,Severe hypersensitivity (e.g., anaphylaxis) to any other beta-lactam antibacterial agents
No significant food interactions; cefaclor can be taken with or without food.,Absorption may be slightly delayed with food but total bioavailability is unaffected.,Avoid grapefruit juice? No known interaction.,Alcohol: No specific interaction, but caution as it may increase side effects like gastrointestinal upset.
No significant food interactions. However, alcohol should be avoided due to potential disulfiram-like reaction (nausea, vomiting, flushing, headache).
First trimester: No increased risk of major congenital malformations based on limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third trimester: No known fetal risks; Cefaclor crosses the placenta with fetal serum concentrations approximately 10-20% of maternal levels.
AVYCAZ (ceftazidime-avibactam) is classified as FDA Pregnancy Category B. Animal reproduction studies in rats and rabbits at doses up to 1.6 times the human dose revealed no evidence of fetal harm. However, there are no adequate and well-controlled studies in pregnant women. Ceftazidime crosses the placenta. Risk cannot be ruled out; use only if clearly needed.
Cefaclor is excreted into human breast milk in low concentrations (M/P ratio approximately 0.05-0.10). Considered compatible with breastfeeding by the American Academy of Pediatrics; use with caution in nursing infants with potential for diarrhea or allergic sensitization.
Ceftazidime is excreted in human milk in low concentrations; avibactam excretion is unknown. The M/P ratio for ceftazidime is approximately 0.02. Caution is advised due to potential disruption of infant gut flora. Consider benefits of breastfeeding versus risk of infant exposure.
No dose adjustment required in pregnancy; pharmacokinetic changes (increased volume of distribution, renal clearance) do not necessitate dose modification due to wide therapeutic index.
No specific dose adjustments are recommended for pregnancy. Physiological changes in pregnancy (e.g., increased volume of distribution, enhanced renal clearance) may alter pharmacokinetics, but data are insufficient to recommend routine dose modification. Monitor clinical response and consider therapeutic drug monitoring if available.
Cefaclor is a second-generation cephalosporin with activity against both Gram-positive and Gram-negative organisms, but not Pseudomonas or MRSA.,It is stable against some beta-lactamases, but resistance can occur via extended-spectrum beta-lactamases (ESBLs).,Dose adjustment is required in renal impairment (Cr Cl <40 m L/min).,It is available as an oral suspension and capsules; suspension must be refrigerated and shaken well before use.,Cefaclor may cause a serum sickness-like reaction, especially in children, characterized by rash, arthralgia, and fever.,It has a short half-life (0.6-0.9 hours) and is usually dosed every 8 hours.,Avoid use in patients with immediate hypersensitivity to penicillins due to cross-reactivity risk (about 10%).
AVYCAZ (ceftazidime-avibactam) is a beta-lactam/beta-lactamase inhibitor combination active against ESBLs, KPC, and OXA-48 carbapenemases. It is not active against metallo-beta-lactamases (e.g., NDM, VIM). Dose adjustment required for creatinine clearance <50 m L/min. Monitor for hypersensitivity reactions, including anaphylaxis. Can cause positive direct Coombs test without hemolysis.
Take this medication exactly as prescribed, usually every 8 hours, with or without food.,Complete the full course of therapy even if you feel better to prevent bacterial resistance.,Shake the oral suspension well before each dose and refrigerate it; discard any unused portion after 14 days.,Contact your healthcare provider if you develop severe diarrhea, rash, joint pain, or fever.,Inform your doctor if you have a history of allergic reactions to penicillins or cephalosporins.,Do not take this medication if you are allergic to cefaclor or any other cephalosporin antibiotic.,If a dose is missed, take it as soon as remembered unless it is almost time for the next dose; do not double the dose.
Take exactly as prescribed; complete full course even if feeling better.,Inform your doctor if you have kidney disease; blood tests may be needed to adjust dose.,Report any signs of allergic reaction (rash, hives, difficulty breathing, swelling).,May cause diarrhea; tell your doctor if severe or persistent.,Avoid alcohol during treatment and for 72 hours after last dose due to possible disulfiram-like reaction.
"Phenindione, a vitamin K antagonist anticoagulant, potentiates the effect of cefaclor, a second-generation cephalosporin antibiotic. Cefaclor may reduce vitamin K production by suppressing intestinal flora, thereby enhancing the anticoagulant effect of phenindione. This interaction can lead to an increased international normalized ratio (INR) and risk of bleeding, particularly in patients with poor nutritional status or prolonged antibiotic therapy."
"Dicoumarol may increase the anticoagulant activities of Cefaclor."
"Warfarin may increase the anticoagulant activities of Cefaclor."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CEFACLOR vs AVYCAZ, answered by our medical review team.
CEFACLOR is a Cephalosporin Antibiotic that works by Bactericidal; inhibits cell wall synthesis by binding to penicillin-binding proteins (PBPs), disrupting peptidoglycan cross-linking.. AVYCAZ is a Cephalosporin Antibiotic that works by AVYCAZ is a combination of ceftazidime, a cephalosporin beta-lactam antibiotic, and avibactam, a non-beta-lactam beta-lactamase inhibitor. Ceftazidime inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis. Avibactam protects ceftazidime from degradation by certain beta-lactamases, including Ambler class A, class C, and some class D enzymes.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CEFACLOR and AVYCAZ depend on the specific clinical indication. These are both Cephalosporin Antibiotic agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of CEFACLOR is: 250-500 mg orally every 8 hours. The standard adult dose of AVYCAZ is: 1 vial (ceftazidime 2g and avibactam 0.5g) IV over 2 hours every 8 hours.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between CEFACLOR and AVYCAZ in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. CEFACLOR is classified as Category A/B. First trimester: No increased risk of major congenital malformations based on limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third t. AVYCAZ is classified as Category C. AVYCAZ (ceftazidime-avibactam) is classified as FDA Pregnancy Category B. Animal reproduction studies in rats and rabbits at doses up to 1.6 times the human dose revealed no eviden. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.